This invention relates generally to boron-carbide-aluminum and other boron-carbide-metal compositions of matter and, more particularly, to boron-carbide-aluminum cermets and other boron-carbide-reactive-metal cermets.
U.S. Pat. No. 2,746,133 by Lowe, U.S. Pat. No. 3,178,807 by Bergmann, U.S. Pat. No. 3,364,152 by Lipp, and U.S. Pat. No. 4,104,062 by Weaver all pertain to boron-carbide-aluminum composites and their manufacture. However, these patents do not show specific cermet compositions or methods for producing directly usable consolidated cermet bodies.
Monolithic ceramic materials have historically been limited in their application as structural materials. This is due to their inherent failure mechanisms which make them very susceptible to microstructural defects such as cracks or voids. One measure of a material's resistance to this type of failure is fracture toughness. Conventional ceramics have low fracture toughness.
One way to increase fracture toughness is through the addition of another ceramic phase, e.g., Al.sub.2 O.sub.3 B.sub.4 C composites, or by the addition of a metal phase, e.g., B.sub.4 C-metal cermets. A cermet is defined as a ceramic-metal composite such that the final microstructure is more than 50 vol. % ceramic phases.
FIG. 1 illustrates the tradeoff of increasing fracture toughness at the expense of increasing specific gravity for some conventional monolithic ceramic materials and a conventional cermet (TiC-Ni-Mo). FIG. 1 also shows how it is possible to move away from the trend of increasing fracture toughness with increasing specific gravity by using selected ceramic-ceramic composites (i.e., Al.sub.2 O.sub.3 -B.sub.4 C) and to a much greater extent by employing selected ceramic-metal composites, in accordance with the present invention, in particular B.sub.4 C-Al or other B.sub.4 C-metal cermets.
Accordingly, it is an object of the invention to provide boron-carbide-aluminum and other boron-carbide-reactive metal cermet compositions.
It is also an object of the invention to provide methods for forming boron-carbide-aluminum and other boron-carbide-reactive metal cermet compositions.
It is another object of the invention to provide boron-carbide-aluminum and other boron-carbide-reactive metal cermet composites with tailorable microstructures and methods for forming same.
It is a further object of the invention to provide boron-carbide-aluminum and other boron-carbide-reactive metal cermet compositions which are fully dense, and methods for forming same.
It is another object of the invention to provide articles of manufacture made from fully dense boron-carbide-aluminum and other boron-carbide-reactive-metal cermet composites.
It is also an object of the invention to provide methods for making boron-carbide-aluminum and other boron-carbide-reactive metal cermet compositions, and articles of manufacture thereof at relatively low cost.